1. Field of the Invention
This invention relates to the injection of fluids having nuclei detectable by NMR measuring devices into wells for purposes of well stimulation, secondary-type oil recovery, reservoir modification, permeability control, and fluid encroachment prevention; and the selection of materials for such uses. More particularly, it relates to the injection of fluids, containing nuclei detectable by NMR detection devices, which interact with the reservoir and/or with fluids in the reservoir in conformance with predetermined criteria.
2. Description of the Prior Art
Pulsed NMR has been used in the field of well logging to determine the presence of hydrocarbons. See U.S. Pat. Nos. 3,456,183, 3,289,072, and 3,528,000; publications by Loren et al, Soc. Petrol. Engrs. Preprint 2529 (1969), Timur et al, Soc. Petrol. Well Logging Analysts Symposium, (May 2-5, 1971); Senturia et al, Soc. Petrol. Engrs. Journal (Sept. 1970), p. 237. In the course of some of these logging processes, fluids having paramagnetic properties have been injected to cancel out the "noise" background of water in the reservoir. Nuclear magnetic resonance has also been utilized in the analysis of a wide variety of liquid-solid systems, e.g. in biology, in geology (in the determination of the water saturation of clays).
Many fluids are used in petroleum production operations which contain nuclei detectable by NMR devices, such as the pulsed NMR detection devices. The fluids used in these processes include semi-polar compounds such as alcohols used as cosurfactants, surfactants of various sorts such as the petroleum sulfonate surfactants and certain polymers. These fluids are used in a variety of processes where fluids are injected into wells drilled into formations. These include injection for corrosion inhibition, U.S. Pat. No. 3,072,192; oil recovery, U.S. Pat. Nos. 3,254,714, 3,261,399, 3,506,070, 3,599,715, and 3,759,325; separation of gas and oil and oil and water interfaces, U.S. Pat. Nos. 3,495,661 and 3,710,861; well stimulation, U.S. Pat. No. 3,568,772; water coning inhibition, U.S. Pat. No. 3,554,288; prevention of salt water encroachment, U.S. Pat. No. 3,587,737; formation fracturing, U.S. Pat. No. 3,603,400; plugging, U.S. Pat. No. 3,604,508, acidizing, U.S. Pat. No. 3,831,679 and in drilling fluids, U.S. Pat. No. 3,734,856. The fact that the processes of the instant invention can be used with such a wide variety of oil field operations makes the invention particularly important.